TPS51513

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SLUS956A – JUNE 2009 – REVISED FEBRUARY 2010

DETAILED DESCRIPTION

Application Circuit List of Materials

Recommended parts for key external components for the circuits in Figure 2 and Figure 3 are in Table 2. These

parts have passed applications tests.

Table 2. Key External Component Recommendations

COMPONENT

MANUFACTURER

PART NUMBER

TI

CSD16409Q3

High-side FET(s)

Infineon

BSC080N03MSG

TI

CSD16401Q5

Low-side FET(s)

Infineon

BSC030N03MSG

Panasonic

ETQP4L series

Tokin

MPCG1040L series

Inductors

Toko

FDUE10140D series

Vishay

IHLP5050 series

Panasonic

EEFSX0D331XE

Bulk output capacitors

Kemet

T528Z series

NEC Proadlizer

PFAF250E127MNS

Panasonic

ECJ2FB0J106K

Ceramic output capacitors

Murata

GRM21BR60J106KE19L

Sense resistor (resistor sensing only)

Panasonic

ERJM1WTJ1M0U

Panasonic

ERTJ1VG103JA

NTC thermistors

TDK

NTCG163JF103HT

Functional Overview

The TPS51513 is a DCAP+™ mode adaptive on-time converter. The output voltage is set using a DAC that

outputs a reference in accordance with either the 3-bit VID code defined in Table 3. VID-on-the-fly transitions are

supported with the slew rate controlled by a single resistor on the ISLEW pin. Powerful integrated FET drivers

support output currents in excess of 25 A. The converter automatically runs in discontinuous mode to optimize

light-load efficiency and battery life. The four switching frequency selections (given in Table 3) enable

optimization of the power chain for the cost, size and efficiency requirements of the design.

Table 3. Frequency Selection Table

TONSEL

GND

250

VREF

300

3.3 V

350

5 V

500

In adaptive on-time converters, the controller changes the on-time as a function of input and output voltage to

maintain a nearly constant frequency during steady-state conditions. In conventional voltage-mode constant

on-time converters, each cycle begins when the output voltage crosses to a fixed reference level. However, in

the TPS51513, the cycle begins when the current feedback reaches an error voltage level which is the amplified

difference between the DAC voltage and the feedback voltage.

This approach has two advantages:

1. The amplifier DC gain sets an accurate linear load-line; this is required for CPU core applications.

2. The error voltage input to the PWM comparator is filtered to improve the noise performance.

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